Many light systems (street lighting systems, flood lighting systems of parking lots, flood lighting systems around buildings, etc.) utilize sodium-vapor lamps.
Sodium-vapor lamps are gas-discharge lamps which create an electrical arc to cause the gas to ionize. Typically sodium-vapor lamps contain a mixture of noble gases (e.g., Neon and Argon). Free electrons, which are the result of the ionization of the gas, collide with the sodium vapor atoms to create yellow light. Low pressure sodium-vapor lamps produce nearly monochromatic yellow light, which is beneficial for reducing light pollution, limiting lighting effects on the environment (for both flora and fauna), and allows for an easier adaption of human eyes to varying light levels. Typical luminous efficiency is 150 lumens per watt.
Metal-halide lamps are typically utilized for wide area overhead lighting situations (e.g., commercial, industrial, and public spaces, such as parking lots, sports arenas, factories, and retail stores) as well as for automotive headlamps. Similar to sodium-vapor lamps, metal-halide lamps are also gas-discharge lamps, but metal-halide lamps produce a substantially white light by creating an electric arc through a gaseous mixture of vaporized mercury and metal halides (compounds of metals with bromine or iodine). As a result, metal-halide lamps have a luminous efficiency of around 75 to 100 lumens per watt. While metal-halide lamps may be used for outdoor light sources, the white light produced by metal-halide lamps create a larger amount of light pollution than that of sodium-vapor lamps. In addition, the human eye takes a longer amount of time to adapt to varying light levels lit by the white light of metal-halide lamps than that of the yellow light of sodium-vapor lamps. Approximately 25% of the energy consumed by the metal-halide lamps is used to produce light, while the remaining 75% of the consumed energy is converted to heat.
Most Gas-discharge lamps, and more specifically, metal-vapor based lamps, require a high amount of energy in the form of heat in order to operate. The heat is used to keep the metal particles in their vapor state, and thus, the high temperature must be maintained within the housing of the lamp in order to keep the metal particles in their vapor state. The present invention embodiment is directed generally to a light system that utilizes both a sodium-vapor LS (first LS) and a metal-halide LS (second LS) to create a light system technology that is more efficient than conventional light source technologies. The present invention embodiment may contain a luminous efficiency of up to 300 lumens per watt. The present invention embodiment utilizes the heat loss of the second LS to increase the efficiency of the first LS in a light system that outputs combined yellow and white lights. In addition, the present invention embodiment may include at least one shroud surrounding the first LS and second LS, whereas at least one shroud contains an infrared (IR) coating to retain the required high temperature within the shroud by reflecting IR radiation back into the shroud.